For example, there is an amplifier as a circuit that outputs a large-amplitude signal to radiate a radio wave from an antenna.
Conventionally, as illustrated in FIG. 1, a circuit has been widely used as an amplifier, which includes N-channel MOS switching transistors 12 and 13, inductor 14, and band pass filter 15, and which uses a pulse waveform signal (transmission signal) amplified by gain control buffer 11 as an input of the amplifier. In addition, the output of the amplifier is radiated from antenna 16.
FIG. 2 is a plan view that illustrates a layout of N-channel MOS switching transistors 12 and 13. In FIG. 2, both ends of gate fingers 21 and 22 are connected to a metal wire (METAL1 in the drawing) having input terminal 25 through which an input signal is input, and both ends of gate fingers 23 and 24 are connected to a metal wire (METAL1 in the drawing) having input terminal 26 through which an input signal is input.
One ends of drains 27 and 28 are connected to output terminal 29, and one ends of sources 30 to 33 are connected to bulk 34 so as to be grounded.
However, in this configuration, the output of the amplifier is a signal of a pulse-like waveform and is a signal containing harmonic components.
In addition, as illustrated in FIG. 3 unlike FIG. 1, there is a pulse-type amplifier using an inverter which includes N-channel MOS switching transistors 12 and 13 and P-channel MOS switching transistors 41 and 42. Even in this configuration, harmonic waves are generated in the output.
Conventionally, in order to avoid odd-order harmonics in particular, a circuit has been proposed in which duty ratios and phases of the pulse waves input from a plurality of amplifiers are independently set, and the outputs of the plurality of amplifiers are combined (see, Patent Literature (hereinafter, abbreviated as PTL) 1, for example).
FIG. 4 is a circuit diagram that illustrates a configuration of the amplifier described in PTL 1, and FIG. 5 is a timing chart that illustrates signal waveforms of the respective portions of the amplifier of FIG. 4. The amplifier of FIG. 4 generates an output signal by combining the output of an inverter which includes N-channel MOS transistor 13 and P-channel MOS transistor 42 and the output of an inverter which includes N-channel MOS transistor 12 and P-channel MOS transistor 41. The duty ratios and the phases of switching transistor input signals S1 to S3 are independently set by duty ratio adjustment and delay adjustment circuit 43 as the voltage waveforms illustrated in FIG. 5, so that the waveform of the output signal is made close to a sine waveform to avoid the odd-order harmonics.